Early larval ontogeny of the Permo‐Carboniferous temnospondyl Sclerocephalus
Early larval ontogeny of the Permo‐Carboniferous temnospondyl Sclerocephalus
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二叠纪石炭纪硬头椎早期幼虫个体发育
DOI：
10.1111/1475-4983.00333
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发表时间：
2003
期刊：
影响因子：
2.6
通讯作者：
R. Schoch
中科院分区：
文献类型：
--
作者：
R. Schoch
硬脑硬脊椎幼虫的早期发育。基于萨尔-纳赫盆地（德国西南部）Lower Rotliegend（二叠纪-石炭纪边界）的 38 个样本进行了分析。该研究重点关注最小的幼虫标本，它们体现了比例和骨化模式的变化。与异形幼虫相比，头骨骨化更充分且速度更快。最小的标本已经完全形成了眶周骨，并进行了缝合。雕刻经历了两个显着的变化，首先是从均匀的凹坑到大小不一、区域分化的凹坑，最后是脊的起源。小幼虫的上颚与较大标本的齿列模式不同，有更多的牙齿，包括培养状突起上的齿状区。首次描述了小幼虫的下颌骨，比成虫的下颌骨更窄，并且具有三个含齿的冠突元件。最小的标本具有骨化不良的神经弓，缺乏椎骨中心，并且肱骨、股骨微弱骨化，以及发育不良的远端元件。后肋骨、后足和指骨出现在胸带的真皮部分之后，而肩胛喙骨和坐骨在整个幼虫期都不存在。四肢和髂骨的早期生长和分化说明了附肢的发育模式，从近端到远端。真皮鳞屑呈均匀的小阶段，由圆形或椭圆形的骨皮组成，具有明显的生长环；在大型幼虫中，它们开始在某些身体区域分化。
The early larval development of the temnospondyl Sclerocephalus sp. is analyzed, based on 38 specimens from the Lower Rotliegend (Permo‐Carboniferous boundary) of the Saar‐Nahe Basin (south‐west Germany). The study focuses on the smallest larval specimens, which exemplify changes in both proportions and ossification patterns. In comparison with dissorophoid larvae, the skull ossifies more fully and at a much faster rate; the smallest specimens already have completely formed circumorbital bones that are sutured throughout. Sculpturing undergoes two marked changes, first from uniformly pitted to pits of variable size and regional differentiation, and finally to the origin of ridges. The palate of small larvae differs from that of larger specimens in patterns of dentition, having more teeth including a denticle field on the cultriform process. The mandible of small larvae is described for the first time, being narrower than in adults and having three dentigerous coronoid elements. The smallest specimens have poorly ossified neural arches, lack vertebral centra, and have faintly ossified humeri, femora, and very poorly developed distal elements. The posterior ribs, metapodia, and phalanges appeared after the dermal elements of the pectoral girdle, whereas the scapulocoracoid and ischium are absent throughout the larval period. Early growth and differentiation of the limbs and the ilium illustrates the developmental patterning of the appendages, which proceeded from proximal to distal. Dermal squamation is uniform in small stages, consisting of round or oval osteoderms with pronounced growth rings; in large larvae, they start to differentiate in certain body regions.